The present invention relates to a technical field of utilizing lignophenol derivatives obtained by phenol-derivatizing lignin, which is one component of timber. More particularly, the present invention relates to the technical field in which molded products are produced using novel materials obtained by further secondarily treating lignophenol derivatives with these materials and molding materials are recovered from the molded product for reuse.
Recently, there has been an increased interest in forest resources that can be continuously used as industrial raw materials, instead of fossil resources, such as petroleum, coal and the like, which have been predicted to be depleted. Such a forest resource, i.e., a lignocellulose resource, is composed of hydrophilic carbohydrates, such as cellulose, hemicellulose and the like, and a hydrophobic lignin (polyphenol), which form the interpenetrating network (IPN) structure and a complicated complex in the cell wall. The lignocellulose resource imparts useful properties to various materials, because of the structure of the complex.
Two methods are known for utilizing the known lignocellulose resource, i.e. timber. One is a direct utilization of the lignocellulose material by cutting or machining the lignocellulose resource, i.e., the complex itself, and processing it into construction materials or furniture building materials having a predetermined shape, or processing the lignocellulose resource into chips or fibers for manufacturing molded products. The other is an indirect utilization of the lignocellulose material by extracting only cellulose, a component of the complex, and making a pulp of the product.
In view of the expected depletion of fossil resources in the future, the reuse of lignocellulose resources is important in the both utilization forms.
However, in the current situation, if a construction material is prepared according to the direct utilization method, it will have a predetermined shape and be comparatively large; therefore, treatments such as grinding and finely-dividing are usually necessary to reuse the construction material. In addition, thermosetting resins used in molded products are difficult to separate from wood chips and fibers. Therefore, in the direct utilization form, after the first use, a portion of the lignocellulose resource is discarded, in many cases without reuse.
Moreover, in the indirect utilization form, only cellulose is recovered and utilized to make a fiber or sheet.
Similarly, in the direct utilization form, the entire lignocellulose resource, i.e., cellulose and lignin, are not reused and, also in the indirect utilization form, lignin, which is one component of the lignocellulose resource, may be reused or not reused under in certain circumstances.
Lignin is an organic substance that exists in large amounts intermingled with cellulose. The present inventor considered the function of lignin as a complex constituting material and previously filed two applications that are directed to extraction of lignin from the lignocellulose resource in a functionalized form. The first application is Japanese Application No. 1-55686 (JP-A 2-233701) and the second application is Japanese Application No. 8-92695 (unpublished as of the filing date of this corresponding International application). The first application teaches methods of bonding a phenol derivative to the lignocellulose resource and, thereafter, contacting the lignocellulose resource with sulfuric acid, whereby lignin is separated from cellulose, because lignin has a bound phenol derivative. In addition, the second application teaches processes for manufacturing a novel cellulose-lignin molded product by using the hybrid lignin, which was provided in the first application, as a binder for a molded cellulose material.
Accordingly, an object of the present invention is to provide novel materials having improved functions that are formed by further secondarily-treating this hybrid lignin and to provide cellulose molded products utilizing these novel materials. In addition, another object is to provide methods for reusing the cellulose molded products by utilizing these novel materials.
In order to accomplish the aforementioned objects, the present inventor made the following inventions.
That is, a first invention is a novel process for producing a lignin derivative, which comprises using a lignophenol derivative containing a diphenylpropane unit formed by binding a carbon atom at an ortho-position relative to a phenolic hydroxyl group of a phenol derivative to a carbon atom at a benzyl-position of a phenylpropane fundamental unit of lignin, and binding an oxygen atom of the hydroxyl group to a xcex2-positional carbon atom under alkali conditions, by which the hydroxyl group can dissociate, to obtain an arylcoumaran derivative containing an arylcoumaran unit in which a coumaran skeleton is bound to an aromatic ring of a phenylpropane unit of lignin. In this invention, the aforementioned phenol derivative is preferably p-cresol.
A second invention is a novel lignin derivative (hereinafter referred to as xe2x80x9can arylcoumaran derivativexe2x80x9d) represented by the following chemical formula and having an arylcoumaran unit in which a coumaran skeleton is bound to an aromatic ring of a lignin phenylpropane unit.

A third invention is a process for producing a novel lignin derivative, which comprises heating a lignophenol derivative containing a diphenylpropane unit formed by binding an aromatic carbon atom of a phenol derivative to a carbon atom at a benzyl-position of a phenylpropane fundamental unit of lignin, with a cross-linking functional group forming compound under alkali conditions, by which the introduced phenolic hydroxyl group of a phenol derivative and/or a phenolic hydroxyl group originally existing in lignin can dissociate, to introduce a cross-linking functional group at an ortho-position and/or a para-position of the phenolic hydroxyl group, thereby obtaining a lignin cross-linking derivative containing a diphenylpropane unit having a cross-linking functional group.
In this invention, preferably, the phenol derivative is p-cresol, the cross-linking functional group forming compound is formaldehyde and the cross-linking functional group is a hydroxymethyl group.
A fourth invention is a novel lignin derivative (hereinafter referred to as xe2x80x9ca lignin cross-linking derivativexe2x80x9d) having a cross-linking functional group at an ortho-position and a para-position of a phenolic hydroxyl group of a lignophenol derivative containing a diphenylpropane unit formed by binding an aromatic carbon atom of a phenol derivative to a carbon atom at a benzyl-position of a phenylpropane fundamental unit of lignin. In this lignin derivative, a preferable cross-linking functional group is a hydroxymethyl group.
A fifth invention is molded products formed by molding fibrous, chip-like, or powdery substrate materials, characterized in that said molded products contain an arylcoumaran derivative.
This molded product has increased strength and water-resistance because of the connection of substrate molding materials using the arylcoumaran derivative. In addition, the arylcoumaran derivative can be easily extracted from a molded product using a solvent having affinity for the arylcoumaran derivative and can be separated from the molding material.
In this invention, the substrate molding material preferably is cellulose fiber, because cellulose fibers are readily available and are easily separated from the arylcoumaran derivative for reuse in a variety of ways.
A sixth invention is a molded product produced by molding fibrous, chip-like, or powdery substrate molding materials, characterized in that said molded product contains the aforementioned lignin cross-linking derivative.
This molded product has increased strength and water-resistance if molding substrate materials are bound by the lignin cross-linking derivative. Preferably, the lignin cross-linking derivatives are cross-linked, because cross-linking further increases strength and water-resistance.
A seventh invention is a method of treating a molded product, which comprises adding a solvent having affinity for this arylcoumaran derivative to a molded product containing the arylcoumaran derivative to recover the arylcoumaran derivative.
According to this invention, the arylcoumaran derivative is a binder material and can be reused and efficiently extracted and separated from a molded product. In addition, using this treatment, a molding substrate material can be reusably separated at the same time.
In this invention, the molding material preferably is cellulose fiber.
When the molding material is cellulose fiber, as a result of treatment with a solvent having affinity for a lignophenol derivative, the cellulose fiber is also readily separated.
Timber, waste timber, end timber, herbaceous plants, agricultural waste and the like can be used as the lignocellulose material and thus, lignocellulose materials are efficiently used and reused.
Further, in this invention, the molding material preferably is cellulose fiber obtained by splitting a lignocellulose material.
When the molding material is a cellulose fiber obtained by splitting a lignocellulose material, a novel molded product is formed using a lignocellulose material. Moreover, cellulose fiber is readily available and is easily separated from a lignophenol derivative, which is utilized again in a variety of ways. In particular, when a lignophenol derivative is obtained from a lignocellulose material, both the cellulose component and the lignin component are efficiently used.